Automatic shift line switchover system for automatic transmission

ABSTRACT

An automatic shift line switchover system for use in an automatic transmission for a vehicle which is responsive to electrical signals representative of the load on the engine and the vehicle speed to provide a shift signal most suitable for the specific shifting condition thereby to operate brake band means and multiple disc clutch means through a hydraulic actuating circuit for carrying out the desired shift.

United States Patent Inventors Mainoru Kawakubo;

Shigehiko Ito, Kariya, both of Japan Appl. No. 64,317 Filed Aug. 17,1970 Patented Dec. 7, 1971 Assignee Nlppondenso Kabushiki KaishaKariya-shi, Aichi-ken, Japan Priority Aug. 18, 1969 Japan 44/65225AUTOMATIC SHIFT LINE SWITCHOVER SYSTEM FOR AUTOMATIC TRANSMISSION 1Claim, 9 Drawing Figs.

U.S. Cl ..317/ 148.511, 74/ 8 6 6 Int. Cl l-l0lh 47/32 B60k 19/00, B661521760 [50] FieldoiSearch 3l7/l48.5

[56] References Cited UNITED STATES PATENTS 3,324,740 6/1967 Lewis et al74/866 3,460,406 8/1969 Strohm et al. 74/866 Primary Examiner-L. T. HixAttorney-Cushman, Darby & Cushman ABSTRACT: An automatic shift lineswitchover system for use in an automatic transmission for a vehiclewhich is responsive to electrical signals representative of the load onthe engine and the vehicle speed to provide a shift signal most suitablefor the specific shifting condition thereby to operate brake band meansand multiple disc clutch means through a hydraulic actuating circuit forcarrying out the desired shift.

AUTOMATIC SHIFT LINE SWITCI-IOVER SYSTEM FOR AUTOMATIC TRANSMISSIONBACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to an automatic transmission for automative vehicles and thelike comprising a,hydraulic torque converter and a multispeed gear unit,and more particularly to an automatic shift line switchover system foruse in such an automatic transmission.

2. Description of the Prior Art In automatic transmissions employedheretofore in common passenger cars, the shift point is generallydetermined from a signal representative of the vehicle speed (taken fromthe output shaft of the multispeed gear unit) or a signal representativeof the revolution of the prime mover or intemal-combustion engine and asignal representative of the negative pressure (boost pressure) in theair intake pipe of theengine or a signal representative of the amount ofdepression of the accelerator pedal by the driver in both the driverange for .driving on a level road and the low range for driving on amountainous road. A commonly employed method comprises obtaining thesesignals in the form of a high and a low fluid pressure, determining theshift point on the basis of the interrelation between these two fluidpressures, and opening or closing related valves by energizing valveactuators for selectively hydraulically operating driving means such asmultiple disc clutch meansand brake band means. Thus, in theconventional automatic transmission which is wholly controlled by meansof fluid pressure, the detected signals inthe form of fluid pressuresare subject to errors and are therefore generally inaccurate. Further,the conventional automatic transmission is defective in that, when thedriver kicks down the accelerator pedal as he wishes a quick shift, acertain length of time is required until the desired. shift can beattained due to the delayed operation of the hydraulic circuit inresponding the detected signals in the form of fluid pressures. Thismeans that the shift point is also frequently subjected to errors.Furthermore, the conventional automatic transmission is defective inthat the hydraulic actuating circuit is generally complexand bulky inconstruction.

SUMMARY OF .T HE INVENTION With a view to overcoming theseprior'defects, it is an object of the present invention to provide anautomatic shift line switchover systemfor use in an automatictransmission for a vehicle which is responsive to application ofelectrical signals representative of the-load on the engine and thevehicle speed to provide a shift signal most suitable for, the specificshifting condition thereby to operate brake band means and multiple discclutch means through a hydraulic actuating circuit for carrying out thedesired shift.

Another object of the present invention is to provide an automatic shiftline switchover system of the above character which includes twoindependent comparing amplifiers each adapted for discriminating betweentwo regions bisected by an automatic shifi line or curve which is afunction of two independent variables so as to select one of theautomaticshift lines in response to an external signal. According to thepresent invention, the desired automatic shift line can be selectedwithout any mutual interference since the two automatic shift lines areidentified by the respective independent comparing amplifiers.Therefore, the output signal from each comparing amplifier can besuitably selected.

A further object of the present invention is to provide an automaticshift line switchover system for use in an automatic transmission for avehicle comprising a signal generator unit for generating signalvoltages which are fixed functions of the vehicle speed and throttleposition for determining a plurality of automatic shift lines, a firstand a second comparing amplifier for carrying out the comparison betweenthe vehicle speed responsive signal and the throttle position responsivesignal applied from said signal generator unit so as to discriminate as.2 to whether the vehicle speed and the throttle position lie in aregion in which an output signal is generated frorn'said comparingamplifiers or in a region inwhich no output signal is generated fromsaid comparing amplifiers, a switching section including two transistorswhich have their collectors connected respectivelyto the outputterminals of said comparing amplifiers and their emitters connected to acommon output tenninal to constitute an emitter follower circuit, aswitch and a transistor circuit in said switching section forselectively applying a switching signal to the input tenninals of saidemitter follower. circuit for selecting one of the output signalsdelivered fromsaid first and second'comparingamplifiers so as toderivethe selectedoutput signal from said output terminal of saidswitching section, and an actuator means connected to said outputterminal of said switching section.

In a conventional system of this kind, only-one comparing amplifier isprovided and the input conditions for the comparing'amplifierare variedto deal with the two shift lines corv respondingto the drive rangeand-the low range, respectively.

ing amplifiers, the vehicle driver can select asuitable automatic shiftline depending on the drivingconditions of the .vehicle running on alevel road, mountainous road or other road so as to attain a shift undera variety of operating conditions.

According tothe presentinvention, the vehicle speed and throttleposition signals can becompared with each other with high accuracydue tothe fact that the comparing amplifiers are employed therein. lnaddition,the'switching section has a very simple structure, is substantially,trouble-free and can operate reliably since the switchover from oneautomatic shift line to the other can be carried out by selectivelyderiving one of the outputs from. the first and second comparingamplifiers. Further, because of the fact that the switching sectionemploys a transistor emitter follower circuit instead of a mechanicalselector switch, noises produced by a spark and the like can be quicklyabsorbed by the emitter follower circuit thereby ensuring an increasedreliability and a rapid switching operation. lf aselector switch weresolely employed in the'system for the purpose of direct switchingoperation, there is'necessarily a period of time during which no outputsignals from the first and second comparing amplifiers can be suppliedto the actuator means. The-present invention eliminates such a drawback.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. la is a block diagram of a firstcomparing amplifier forming part of an automatic shift line switchoversystem for an automatictransmission according to the present invention.

FIG. 1b isan automatic shift diagram illustrating the operation of thefirst comparing amplifier shown in FIG. la.

FIG. 2a is a, block diagram of a second comparing amplifier forming partof the system according to the present invention.

FIG. 2b isan automatic shift diagram illustrating the opera- .tion ofthe second comparing amplifier shown in FIG. 2a.

used in an automatic shift line switchover system for an automatictransmission according to the present invention. An authe input voltagex is larger than the input voltage y in there gion B, then all thecoordinates in the region A satisfy the relation x' y, and all thecoordinates in the region B satisfy the relation x' An out ut si nal lis delivered from detefmmed slgnals apphed the second comgaring amiiifier C, when the relation x' y' is comparing amphfier w f f Itsatisfied, while an output signal z= is delivered from the be seen thatthe automziuc i h 15 generally m the form second comparing amplifier Cwhen the values of the vehicle. ofa curve The autorfauc i I hes on a fdefined by speed V and the throttle position 9 fall within the region Bin two axes representative of two independent variables such as 10 whichthe relation Xl y is satisfied. vehicle speed V and throttle position 9and bisects the plane i two regions A d A input voltage V) which is aThe present invention is featured by the fact that the output function fthe vehicle speed v and an input voltage y=g1(9) signals delivered fromthe comparator composed of the comwhich is a function of the throttleposition 6 are applied to a paring amplifiers l and 2 are Switched Overby a switching noninverted input tetminai 2 and an inverted inputterminal 1 5 section so as to select one of the automatic shift lines.Refer- 2b, respectively, of the fir t comparing lifi Ch and a ring toFIG. 3, an embodiment of the present invention comy output signal z= pt1 pp at the output rhinit s ls stam aulss safisisaa.xekasssi a minal 2cof the first comparing amplifier C depending on the dctcrminins theautomatic Shift lines. a comparator relative magnitude of the in utvoltages x and y. Here, 1" s i hing tion an mplifie m an 4. nd n ctua ormeans that asignal is delivered from the comparing amplifier means 5such as a solenoid or motor for actuating the valve in C,, while 0 meansthat no signal is delivered therefrom. A the automatic transmission TheSignal Eehctator 1 point P on the coordinate plane in FIG. lb isrepresented by gcncratcs two Signal ge X and X' which r ea 8 fixed thecorresponding values of the throttle position 9 and the function theVehicie Speed v and two Signal Voltages and vehicle speed V. The shiftline l bisecting this plane represents which are each a fixed fuhctiohof the throttle Position a coordinate group where the input voltages atand y applied to comparator 2 includes a first comparihB amplifier Ctand the first comparing amplifier C are equal to each other. Thus, aSecond mp g amplifier 2 of the kind described with the relation x=y,hence, f V)=g,(6) holds on the shift line I. fefeieme t0 FiGS- and Thfifirst comparihfl amplifier i Suppose that the input voltage x is smallerthan the input voltdelivers n ou put ignal 2 by comparing the inputvoltage a age y in the region A, and the input voltage x is larger thanthe with the input Voltage .V with high precisioht white the inputvoltage y in the region B, then all the coordinates in the comparingamplifier 2 deiivets an output siflhai y p region A satisfy the relationx y, and all the coordinates in the s the input Voltage w the p Voltage3" with B region B satisfy the relation x y. An output signal z=0 isPrecisiondehveted from the first comparing amplifier l when the Feta"The operation of the system of the present invention zfi'n tion X y i5Satisfied, while an output sighai i is delivered FIG. 3 will bedescribed with reference to FIGS. lb and 2b. from the first comparingamplifier C when the values of the Ref i to FIG. 1b, it is supposed thata point P, (V,, 9,) lies vehicle speed V and the throttle position 9fall within the rein the region A on one side of the automatic shiftline I, and a gion B in which the relation x y is satisfied. point 0,,(V 8,) corresponding to the point P (V 6,) lies In thete is Show"comparing amplifier 2- also in the region A in FIG. 2b. in this case, anoutput signal An automatic shift line ii determined by signals appliedto the 40 is delivered f the f r t comparing a lifi r Ch while secondcomparing amplifier C, is shown in F IG. 2b. Like the an output i l 5: ii d li d f h second comps. shift line i described above, the shift lineI] lies on a plane in; m lifier C as described previously. The outputsignal defined by two axes representative of the two independent d li df h fi comparing lifi C i li d to variables V and 9 and bisects thePlane into two regions the amplifier means 4 to be amplified therein soas to energize and P Voltage f2( which is a function of the the actuatormeans 5 when the switching section 3 is in'a posi- VehiCte speed v andan input Voltage y' 8z( which is a function 5, as shown. it is to benoted that the phase of the input to tion Of the throttle position 6 areapplied [0 an inverted input the amplifier means 4 is so elected thatthe actuator means 5 terminal 2b and a noninverted input terminal 20',respectivei giz d i re to th ut ut i nal deli e ed ly, of the secondcomparing amplifier C and a binary output 'from the first comparingamplifier C,. When the point P, signal z'=0" or l appears at the outputterminal 20' demoves into the region B in FIG. lb, an output signal z=l"is pending on the relative magnitude of the input voltages x and nowdelivered from the first comparing amplifier C, with the y A poi 0 o theordin e pla n F G. 2b is result that the actuator means 5 isdeenergized. The point Q, represented by the corresponding values of thethrottle posilies in the region A when the point P, lies in the regionA. tion 9 and the vehicle speed V. The shift line ll bisecting thisThus, an output signal z'= i is delivered f the second plane representsa coordinate group where the input voltages comparing amplifier C to beapplied to the amplifier means 4 x' and y are applied to the secondcomparing amplifier C, are to deenergize the actuator means 5 when theswitching section equal to each other. Thus til e reiation y', hence, fV) 3 is in a position S in FIG. 3.-The above relation is tabulated =g (6holds on the shift line 1]. Suppose that the input volti h f ll i blOutput Output from from Coordinates Coordinates comparing comparingSwitching Actuator in Fig. lb, in Fig. 2b, amplifier amplifier section tmeans o( o, o) QoWn, Ci, 2 C 2 3 5 Region A Region A. "0" "1 S1 EnergizeS; De-energized.

Region B Region A. "1 1" S Die-energized.

S3 Dre-energized.

Region A Region B- "0" 0" S Energized.

S Energized.

Region B Region B "1 0 S De-energized.

S1 Energized.

Another embodiment of the present invention shown in FIG. 4 is generallysimilar to the embodiment shown in FIG. 3

except that the switching means in the switching section 3 in the latteris replaced by transistors. Like reference numerals comparing amplifierC The presence of a point P (V, 6) in either of the regions A and B inFIG. lb is identified by the appearance of l or from the first comparingamplifier C, depending on the relative magnitude of input voltage x andy. Similarly, the presence of a point Q (V, 6) in either of the regionsA and B in FIG. 2b is identified by the appearance of 1 or O from thesecond comparing amplifier C, depending on the relative magnitude ofinput voltages at and y. The input voltages x=f, (V) and y=g,(6) areapplied to a nonin verted input terminal 2a and an inverted inputterminal 2b, respectively, of the first comparing amplifier C,, whilethe input voltages y =g,(6) and x =,f,( V) are applied to a noninvertedinput terminal 2a andian inverted input terminal 2b, respectively, ofthe second comparing amplifier C,. An output;

signal z=l" appears at the output terminal 20 of the first comparingamplifier C, when x y (region B), while an output signal z=o appears atthe outputterminal 2c when x y (region A). Similarly, an output signalz="o"appears at the output terminal 20' of thesecond comparing amplifierC, when x' y' (region B), while an. output signal z'= appears at theoutput terminal 2c when x' y' (region A A switching section 3 includes apair of transistors 3a and 3b which have their emitters connected incommon to one end of a load resistor 3c which is grounded at the otherend thereof. The collectors of the transistors 3a and 3b are connectedto the output terminals 2c and 2c of 'the respective comparingamplifiers C, and C,. An amplifying, shaping and switching circuit 3d isconnected at its input side to a power supply 3f through a selectorswitch 3e. A switching circuit 3 is connected at its input side to theoutput side of the amplifying, shaping and switching circuit 3d and actsto invert the output from the amplifying, shaping and switching circuit3d. The output terminal 3h of the switching section 3 is connected to anactuator means through an amplifier means 4. The base of the transistor3a is connected to the output side of the amplifying, shaping andswitching circuit 3d, while the base of the transistor 3b is connectedto the output side of the switching circuit 3g. Because of such anarrangement, the switching signal is applied to only one of the bases ofthe transistors 3a and 3b. In the open position of the switch 3e, theamplifying, shaping and switching circuit 3d delivers an output signalnF I," and therefore, an output signal 'nT=0" is delivered from theswitching circuit 3g. As a result, the transistor 3a conducts by beingurged by the output voltage supplied from theamplifying, shaping andswitching circuit 3d, while the transistor 3b is cut off. In thisinstance, the output signal delivered from the first comparing amplifierC, is a sole output signal delivered from the comparator 2 and appearsacross the load resistor 30, while the output signal delivered from thesecond comparing amplifier C, cannot appear due to the cutoff of thetransistor 3b. On the other hand, when the switch Be is urged-to theclosed position and the voltage of the power supply 3f is applied to theinput side of the amplifying, shaping and switching circuit 3d, anoutput signal m=0," or no .output signal is delivered from theamplifying, shaping and switching circuit 3d and an output signal r7=" lis delivered from the switching circuit 3g, with the result that thetransistor 3a is cut off and the transistor 3b conducts. Thus, theoutput signal delivered from the second comparing amplifier C, appearsacross the load resistor 3c, and the signal appearing across the loadresistor 3c is independent of any variation in the output signaldelivered from the first comparing amplifier C,. The output signaldelivered from the comparing amplifier C, or C and appearing across theresistor 3c depending on the position of the switch 3c is applied to theamplifier means 4 and is amplified by the amplifier means 4 to beapplied to the actuator means 5 which may be a motor or solenoid. Theamplifier means 4 includes a oluralitv of am lification sta es. Theamplifier means 4 employed in the embodiment shown in FIG. 4 is suchthat it energizes the actuator means 5 when 0" appears across theresistor 30 and deenergizes the actuator means 5 when l appears acrossthe resistor 30. I

FIG. 5 is an electrical circuit diagram of a further embodimentof thepresent invention, and FIGS. 6 and 7am automatic shift diagrams-showing.automatic'shift lines determined depending on the signals deliveredfrom a signal generator unit 1. In FIGS. 6 and 7, the vehicle speed V inkilometers per hour and the throttle position 6 in degrees are taken asindependent variables, and the automatic shifilines I and II are givenby straight lines passing through the origin.

1 Referringto FIG. 5 wherein like-reference numerals are used to denotelike vparts appearing'in FIG. 4, the signal generator unit 1 includes atachogenerator 21 for generating a signal representative of thevehiclespeed, a.diode 22 and a capacitorv23; The AC voltage generated bythe tachogenerator 21 is rectified by-the diode 22 so that's-voltageproportional to the-vehicle speed V appears across the capacitor 23.

Variable-resistors 24 and. 25 divide the terminal voltage of thecapacitor 23. Suppose that the'voltage division ratio of the variableresistor 24 is k,, then an inputvoltage x lql is .applied to aninverted. input terminal 2a of a. first comparing amplifier C,. Supposefurther that the voltage division=ratio of the variableresistor 25' is-k,, then an input voltage x'-k,V is applied to a noninverted inputterminal 21: of a secondcomparing amplifier C,. Variable resistors 29and 30 are connected to v .a power supply 28 and cooperate with means.responsive to the throttle position 6 so as to convertthethrottleposition into a corresponding voltage. Suppose that thevoltage division ratio of the variable resistor 29 is m,, thenaninputvoltage y=m',6 is applied-to anoninverted input terminal 2!: of thefirst comparing amplifierC -Suppose further: that the voltage division.ratioof the variable resistor 30 ism,,-then an input voltage y'=m,8isapplied-to an inverted input 'terminallaof the second comparingamplifier C,. Whilethe .variable resistors 29 and-.30 of -thetype inwhich theresistance value is continuously variable are'shown herein byway of example they may be resistors whose-resistance value isdiscontinuously varied by a plurality of lead switches which aresuccessively closed by a magnet rotating with the throttle shaft. Inthislatter case, a stably operating device can be provided by. virtue of thehysteresis characteristic of the lead switches. Further, a feedbackcircuit may be provided between the output terminal 20 and the. invertedinput terminal 2a of the comparing amplifier C, so as to utilize thehysteresis relative to the vehicle speed.

In response to application of the two input signals x=k,V and y=m,9 tothe first comparing amplifier C,, an output signal z l is deliveredtherefrom when x y, hence, k,V m,9,' while an output signal z="0" isdelivered therefrom when x y, hence, k,V m,8. Referring to FIG; 6, ashift occurs at a vehicle speed V, when the throttle-position is 6,.Thus, by setting oneof k,and m, at a suitable value, the other can besoughtfrom the equation k,V,,=m,6,,. The automatic shift line I in FIG.6 is a straight line represented by the equation a fi 1 and thecoordinate plane defined by the vehicle speed V and the throttleposition 9 is bisected by the automatic shifl line I into a regiOn Awherein the output signal z is 0" and a region B wherein the outputsignal 2 is l As the driving conditions of the vehicle make a shift froma point Q,(9,, V,) satisfying the relation er C, changes from 0 to l ata point Q1( 6,, V,) satisfying the relation The same applies to thesecond comparing amplifier C In response to the application of the twoinput signals x'=k,V and y'=m 9 to the second comparing amplifier C anoutput signal z'="0" is delivered therefrom when x' y', hence, k V m,6,while an output signal z'=l" is delivered therefrom when .x' y', hence,k V m 9. Referring to FIG. 7, a shift occurs at a vehicle speed V whenthe throttle position is 9 Thus, by setting one of k, and m at asuitable value, the other can be sought from the equation k, V,,=m,6,,.The automatic 2 1 r 61 m2V to a point 0,78,, V satisfying the relation 20 I I a v.

the output signal z delivered from the second comparing amplifier C,changes from 1" to 0" at a point Q,(9 V satisfying the relation Aswitching section 3 includes an automatic shift line selector switch 32cooperating with the change lever, a power supply 31, resistors 33, 34,36, 37, 38 and 40, and transistors 35 and 39 for effecting theamplification and inversion of the switching signal depending on theposition of the switch 3e. Transistors 3a and 3b are operative toselectively derive the outputs from the comparing amplifiers C, and CThe collector of the transistor 3a is connected to the output terminal2c of the first comparing amplifier C,, while the collector of thetransistor 3b is connected to the output terminal 2c of the secondcomparing amplifier C The emitters of these transistors 3a and 3b areconnected in common to one end ofa resistor 3:, hence, to an outputterminal 3h, and the other end of the resistor 3c is grounded toconstitute an emitter follower circuit. The bases of the transistors 3nand 3b are connected to the collectors of the transistors 35 and 39through resistors 41 and 42, respectively. The signal appearing acrossthe resistor 30 is applied to the base of a transistor 47 in anamplifier means 4 through a resistor 46. The transistor 47 has a loadresistor 48 connected therewith. The collector of the transistor 47 isconnected to the base of a transistor 49. An actuator means 5 isconnected to the collector of the transistor 49 and includes a solenoid50 and a diode 51 for suppressing the voltage induced in the solenoid50. The transistors 47 and 49 have their emitters grounded, and a powersupply 52 supplies power to the transistors 47 and 49 and to theactuator means 5. The comparing amplifiers C, and C, are also connectedto a power supply (not shown).

The operation of the automatic shift line switchover system shown inFIG. 5 will be described with reference to the automatic shift diagramsshown in FIGS. 6 and 7. The system according to the present inventiongives such instructions that the gear unit in the transmission takes thelow gear position when the vehicle speed V and the throttle position 9lie in the region A in FIG. 6 and the high gear position when thevehicle speed V and the throttle position 6 lie in the region B in FIG.6. The solenoid 50 is energized in the low gear position and isdeenergized in the high gear position. Similarly, the system gives suchinstructions that the gear unit in the transmission takes the low andthe high gear position, respectively, when the vehicle speed V and thethrottle position 9 lie in the regions A and B in FIG. 7. In this lattercase, however, the operation of the solenoid 50 is contrary to the caseof FIG. 6 so that the solenoid is deenergized in the low gear positionand energized in the high gear position. The mechanical operation forshifting the gear between low and high gear is associated with theposition of the switch 3e.

The selector switch 3e is in the open position when 6717651 cle runs ona level road. Due to the open position of the switch 3e, the transistor35 is cut off and the transistor 39 conducts with the result that thetransistor 3a conducts and the transistor 3b is cut off. The voltage ofthe power supply 31 is selected to be higher than the voltage appearingacross the resistor 30 when the output signals 2, and z delivered fromthe comparing amplifiers C, and C, are l Thus, current is supplied fromthe first comparing amplifier C, to the resistor 3c through thetransistor 3a, but no current is supplied from the second comparingamplifier C to the resistor 30 due to the fact that the transistor 3b iscutoff. Suppose now that the vehicle speed V and the throttle position 9have respective values of V, and 9, represented by the point Q,(V,, 9,)lying in the region A in FIG. 6, then it is apparent from the previousdescription that the relation hence, y,=m,8, x,=k,V, holds at this point0,. Since, in this case, the relation y x holds between the inputvoltages applied to the first comparing amplifier C,, the output signal2 is "0 and no voltage appears across the resistor 3c. As a result, thetransistor 47 is cut off and the transistor 49 conducts to energize thesolenoid 50 so that the gear unit in the transmission takes the low gearposition. As the vehicle speed V and the throttle position 9 vary fromthe point Q, to the point Q, via the point Q, in FIG. 6, the relation yx between the input voltages x and y applied to the first comparingamplifier C, is changed to the relation y x at the transition point 0,,and the output signal 2 delivered from the comparing amplifier C, ischanged from 0" to l." Thus, l" appears across the resistor 3c so thatthe transistor 47 conducts and the transistor 49 is cutoff. This resultsin the deenergization of the solenoid 50 and the gear unit in thetransmission is shifted to high gear.

The selector switch 32 is in the closed position when the vehicle runson a mountainous or like road. Due to the closed position of the switch32, the transistor 35 conducts and the transistor 39 is cut off with theresult that the transistor 3a is cut off and the transistor 3b conducts.In this state, an output signal 2' is delivered from the secondcomparing amplifier C, to appear across the resistor 3c. Suppose nowthat the vehicle speed V and the throttle position 6 have respectivevalues of V, and 9, represented by the point Q,'(V,, 8,) lying in theregion A in the automatic shift diagram shown in FIG. 7, then it isapparent from the previous description that the relation hence,y,'=m,9,' x,=k,V, holds at this point 0,. Since, in this case, therelation y' x' holds between the input voltages applied to the secondcomparing amplifier C,, the output voltage z' is 1 and this voltageappears across the resistor 30. As a result, the transistor 47 conductsand the transistor 49 is cut off to deenergize the solenoid 50 so thatthe gear unit in the transmission takes the low gear position. As thevehicle speed V and the throttle position 8 vary from the point 0, tothe point Q, via the point Q, in FIG. 7, the relation y' x' between theinput voltages x and y applied to the second comparing amplifier C, ischanged to the relation y'y x' at the transition point 0,, and theoutput signal z delivered from the comparing amplifier C, is changedfrom "1 to 0." Thus, 0" appears across the resistor 30 so that thetransistor 47 is cut off and the transistor 49 conducts. This results inthe energization of the solenoid 50 and the gear unit in thetransmission is shifted to high gear. The above operation is tabu- Vlated in the following table:

The embodiments described above have referred to an application of thesystem of the present invention to a two-forward speed automatictransmission. However, the system can be easily applied to athree-forward speed automatic transmission. In this instance, the systemshown in FIG. may further include a third comparing amplifier, a 2-3shift actuator means, a variable resistor connected in parallel with thevariable resistors 24 and 25, and a variable resistor connected inparallel with the variable resistors 29 and 30 so that two voltagesobtained by these additional variable resistors may be supplied to thethird comparing amplifier to energize the 2-3 shift actuator means bythe output signal delivered from the third comparing amplifier when the2-3 shift is required. in this system, arrangement may be such that thesecond speed can be obtained when the l-2 shift actuator means 5 issolely energized, the third speed can be obtained when both the 1-2shift actuator means 5 and the 2-3 shift actuator means are energized,and the first speed can be obtained when both the actuator means aredeenergized.

in the embodiments described above, the solenoid 50 is energized anddeenergized respectively to obtain the first and the second speed in thedrive range, while it is deenergized and energized respectively toobtain the first and the second:

speed in the low range. However, the manner of the operation of thecomparing amplifiers may be changed so that the energization anddeenergization of the solenoid 50 give the first (or second) and second(or first) speed in both the drive range and the low range.

We claim:

1, An automatic shift line switchover system for use in an automatictransmission for a vehicle comprising a signal generator unit forgenerating signal voltages which are fixed functions of the vehiclespeed and throttle position for determining a plurality of automaticshift lines, a first and a second comparing amplifier for carrying outthe comparison between the vehicle speed responsive signal and thethrottle position responsive signal applied from said signal generatorunit so as to discriminate as to whether the vehicle speed and thethrottle position lie in a region in which an output signal is generatedfrom said comparing amplifiers or in a region in which no output signalis generated from said comparing amplifiers, a switching sectionincluding two transistors which have their collectors connectedrespectively to the output terminals of said comparing amplifiers andtheir emitters connected to a common output terminal to constitute anemitter follower circuit, a switch and a transistor circuit in saidswitching section for selectively applying a switching signal to theinput terminals of said emitter follower circuit for selecting one ofthe output signals delivered from said first and second comparingamplifiers so as to derive the selected output signal from said outputterminal of said switching section, and an actuator means connected tosaid output terminal of said switching section.

1. An automatic shift line switchover system for use in an automatictransmission for a vehicle comprising a signal generator unit forgenerating signal voltages which are fixed functions of the vehiclespeed and throttle position for determining a plurality of automaticshift lines, a first and a second comparing amplifier for carrying outthe comparison between the vehicle speed responsive signal and thethrottle position responsive signal applied from said signal generatorunit so as to discriminate as to whether the vehicle speed and thethrottle position lie in a region in which an output signal is generatedfrom said comparing amplifiers or in a region in which no output signalis generated from said comparing amplifiers, a switching sectionincluding two transistors which have their collectors connectedrespectively to the output terminals of said comparing amplifiers andtheir emitters connected to a common output terminal to constitute anemitter follower circuit, a switch and a transistor circuit in saidswitching section for selectively applying a switching signal to theinput terminals of said emitter follower circuit for selecting one ofthe output signals delivered from said first and second comparingamplifiers so as to derive the selected output signal from said outputterminal of said switching section, aNd an actuator means connected tosaid output terminal of said switching section.